The use of encryption by network traffic is increasing rapidly. Notably, transport layer security (TLS), opportunistic encryption, the availability of free public key infrastructure (PKI) certificates, and other factors, have led to a significant rise in encrypted Internet traffic. In addition, more and more protocols are using encryption for privacy purposes and to ensure security from attackers. For example, version 2 of the Hypertext Transfer Protocol (HTTP/2.0) strongly recommends the use of TLS, resulting in many websites now transitioning from using HTTP to using HTTP Secure (HTTPS).
Traditionally, some networks use traffic inspection techniques, to prioritize traffic flows in the network. For example, access networks often have insufficient bandwidth and constrained resources, thereby preventing some applications from functioning as well as desired. Although the quality of wireless and wired access networks continues to improve, resources in such networks remain constrained for various reasons. Thus, access networks and other networks with constrained resources often attempt to classify and prioritize their traffic flows using deep packet inspection (DPI) and/or Internet Protocol (IP) address lists. For example a device in an access network may use DPI to identify and prioritize one-way video streaming over file-transfer. However, DPI may not be available to the device, if the corresponding traffic flow is encrypted, thereby preventing the device from gleaning information about the flow for purposes of prioritizing the flow.